Buggy code:
private boolean commentStartsBlock ( int start , int end ) { } private ASTNode [ ] computeMergedMemberDeclarations ( ASTNode [ ] nodes ) { } private ASTNode [ ] computeMergedMemberDeclarations ( TypeDeclaration typeDeclaration ) { } private boolean dumpBinaryExpression ( BinaryExpression binaryExpression , int operator , BlockScope scope ) { } private boolean dumpEqualityExpression ( BinaryExpression binaryExpression , int operator , BlockScope scope ) { } private final TextEdit failedToFormat ( ) { } private void format ( AbstractMethodDeclaration methodDeclaration , ClassScope scope , boolean isChunkStart , boolean isFirstClassBodyDeclaration ) { } private void format ( FieldDeclaration fieldDeclaration , ASTVisitor visitor , MethodScope scope , boolean isChunkStart , boolean isFirstClassBodyDeclaration ) { } private void format ( CodeFormatterVisitor . MultiFieldDeclaration multiFieldDeclaration , ASTVisitor visitor , MethodScope scope , boolean isChunkStart , boolean isFirstClassBodyDeclaration ) { } public TextEdit format ( String string , ASTNode [ ] nodes ) { } public TextEdit format ( String string , CompilationUnitDeclaration compilationUnitDeclaration ) { } public TextEdit format ( String string , ConstructorDeclaration constructorDeclaration ) { } public TextEdit format ( String string , Expression expression ) { } private void format ( AnnotationTypeDeclaration annotationTypeDeclaration ) { } private void format ( TypeDeclaration typeDeclaration ) { } private void format ( TypeDeclaration memberTypeDeclaration , ClassScope scope , boolean isChunkStart , boolean isFirstClassBodyDeclaration ) { } private void format ( EnumDeclaration enumDeclaration , ClassScope scope , boolean isChunkStart , boolean isFirstClassBodyDeclaration ) { } private void formatAnonymousTypeDeclaration ( TypeDeclaration typeDeclaration ) { } private void formatBlock ( Block block , BlockScope scope , String block_brace_position , boolean insertSpaceBeforeOpeningBrace ) { } private void formatCascadingMessageSends ( CascadingMethodInvocationFragmentBuilder builder , BlockScope scope ) { } private void formatClassBodyDeclarations ( ASTNode [ ] nodes ) { } private void formatEmptyTypeDeclaration ( boolean isFirst ) { } private void formatGuardClauseBlock ( Block block , BlockScope scope ) { } private void formatLeftCurlyBrace ( final int line , final String bracePosition ) { } private void formatLocalDeclaration ( LocalDeclaration localDeclaration , BlockScope scope , boolean insertSpaceBeforeComma , boolean insertSpaceAfterComma ) { } private void formatMessageSend ( MessageSend messageSend , BlockScope scope , Alignment messageAlignment ) { } private void formatMethodArguments ( AbstractMethodDeclaration methodDeclaration , boolean spaceBeforeOpenParen , boolean spaceBetweenEmptyParameters , boolean spaceBeforeClosingParen , boolean spaceBeforeFirstParameter , boolean spaceBeforeComma , boolean spaceAfterComma , int methodDeclarationParametersAlignment ) { } private void formatEnumConstantArguments ( EnumConstant enumConstant , boolean spaceBeforeOpenParen , boolean spaceBetweenEmptyParameters , boolean spaceBeforeClosingParen , boolean spaceBeforeFirstParameter , boolean spaceBeforeComma , boolean spaceAfterComma , int methodDeclarationParametersAlignment ) { } private void formatNecessaryEmptyStatement ( ) { } private void formatOpeningBrace ( String bracePosition , boolean insertSpaceBeforeBrace ) { } private void formatStatements ( BlockScope scope , final Statement [ ] statements , boolean insertNewLineAfterLastStatement ) { } private void formatThrowsClause ( AbstractMethodDeclaration methodDeclaration , boolean spaceBeforeComma , boolean spaceAfterComma , int alignmentForThrowsClause ) { } private void formatTypeMembers ( TypeDeclaration typeDeclaration ) { } private void formatTypeOpeningBrace ( String bracePosition , boolean insertSpaceBeforeBrace , TypeDeclaration typeDeclaration ) { } private int getDimensions ( ) { } private boolean hasComments ( ) { } private boolean isNextToken ( int tokenName ) { } private boolean isClosingGenericToken ( ) { } private boolean isGuardClause ( Block block ) { } private boolean isMultipleLocalDeclaration ( LocalDeclaration localDeclaration ) { } private boolean isPartOfMultipleLocalDeclaration ( ) { } private void manageClosingParenthesizedExpression ( Expression expression , int numberOfParens ) { } private void manageOpeningParenthesizedExpression ( Expression expression , int numberOfParens ) { } public boolean visit ( AllocationExpression allocationExpression , BlockScope scope ) { } public boolean visit ( AND_AND_Expression and_and_Expression , BlockScope scope ) { } public boolean visit ( AnnotationTypeDeclaration annotationTypeDeclaration , BlockScope scope ) { } public boolean visit ( AnnotationTypeDeclaration annotationTypeDeclaration , ClassScope scope ) { } public boolean visit ( AnnotationTypeDeclaration annotationTypeDeclaration , CompilationUnitScope scope ) { } public boolean visit ( AnnotationTypeMemberDeclaration annotationTypeMemberDeclaration , ClassScope scope ) { } public boolean visit ( Argument argument , BlockScope scope ) { if ( ( argument . modifiers ) != ( CodeFormatterVisitor . NO_MODIFIERS ) ) { this . scribe . printComment ( ) ; this . scribe . printModifiers ( argument . annotations , this ) ; this . scribe . space ( ) ; } if ( ( argument . type ) != null ) { argument . type . traverse ( this , scope ) ; } <START_BUG> if ( argument . isVarArgs ) { <END_BUG> this . scribe . printNextToken ( TerminalTokens . TokenNameELLIPSIS , this . preferences . insert_space_before_ellipsis ) ; if ( this . preferences . insert_space_after_ellipsis ) { this . scribe . space ( ) ; } this . scribe . printNextToken ( TerminalTokens . TokenNameIdentifier , false ) ; } else { this . scribe . printNextToken ( TerminalTokens . TokenNameIdentifier , true ) ; } int extraDimensions = getDimensions ( ) ; if ( extraDimensions != 0 ) { for ( int i = 0 ; i < extraDimensions ; i ++ ) { this . scribe . printNextToken ( TerminalTokens . TokenNameLBRACKET ) ; this . scribe . printNextToken ( TerminalTokens . TokenNameRBRACKET ) ; } } return false ; } public boolean visit ( ArrayAllocationExpression arrayAllocationExpression , BlockScope scope ) { } public boolean visit ( ArrayInitializer arrayInitializer , BlockScope scope ) { } public boolean visit ( ArrayQualifiedTypeReference arrayQualifiedTypeReference , BlockScope scope ) { } public boolean visit ( ArrayQualifiedTypeReference arrayQualifiedTypeReference , ClassScope scope ) { } public boolean visit ( ArrayReference arrayReference , BlockScope scope ) { } public boolean visit ( ArrayTypeReference arrayTypeReference , BlockScope scope ) { } public boolean visit ( ArrayTypeReference arrayTypeReference , ClassScope scope ) { } public boolean visit ( AssertStatement assertStatement , BlockScope scope ) { } public boolean visit ( Assignment assignment , BlockScope scope ) { } public boolean visit ( BinaryExpression binaryExpression , BlockScope scope ) { } public boolean visit ( Block block , BlockScope scope ) { }

Fix:
if ( argument . isVarArgs ( ) ) {